Studies on the role of platelet membranes in hemostatis will focus on the possible role of glycosyltransferases in adhesion and aggregation, including the possible role of lipid intermediates, Factor VIII, and complement. Spin labeling and electron paramagnetic resonance will be carried out to study the sites of binding of ADP and of divalent cations while ferritin-conjugated lectins will be used to determine the distribution of specific glycoprotein sites on the platelet surface in response to aggregating agents. The energetics of aggregation will be studied by microcalorimetry.